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Biomedical subjects

P Albrecht

Publications and source records attributed to P Albrecht.

At least 73 records · Page 4Linked to original sources
PubMed1989

Modulation of cardiac autonomic activity during and immediately after exercise.

Fluctuations in heart rate above 0.03 Hz reflect autonomic modulation of sinoatrial node activity. To assess the dynamics of autonomic nervous activity during and immediately after exercise, we determined the power spectrum of heart rate and respiratory fluctuations in 43 normal subjects without known cardiac disease, 8 patients with severe congestive heart failure, and 6 patients status-post cardiac transplantation before, during, and after graded-work load exercise on a cycle ergometer. Before exercise, heart rate fluctuations (spectral power) at both high (0.15-0.80 Hz) and low (0.03-0.15 Hz) frequencies were significantly higher in normal subjects than in either heart failure or transplant patients but were not different between the two groups with heart disease. During exercise, heart rate power at all frequencies rapidly and progressively decreased in normal subjects, until at peak exercise it was not different from the other two groups. During recovery, heart rate power increased in normal subjects but remained significantly below base line. The findings demonstrate a marked reduction of autonomic modulation of heart rate in patients with heart failure and after cardiac transplant and support a progressive withdrawal of vagal activity during exercise with a gradual increase during recovery in normal subjects.

Adolescent↗
PubMed1989

Low-frequency oscillations in arterial pressure and heart rate: a simple computer model.

We have previously reported that low-frequency oscillations in arterial blood pressure (ABP) and heart rate (HR) occur when conscious dogs experience severe blood loss. These low-frequency oscillations are generated by enhancement of the sympathetic nervous system and inhibition of the parasympathetic nervous system. We have developed a simple computer model to elucidate those properties critical to the generation of these oscillations. Our model incorporates several important features: 1) arterial baroreceptor feedback loops, which relate ABP to targeted HR and total peripheral resistance (TPR) values; 2) two effector outputs, HR and TPR, which are controlled by the outputs of vagal, beta-adrenergic, and alpha-adrenergic effector mechanisms; 3) a fixed beat-to-beat stroke volume; and 4) a wind-kessel model, which represents the peripheral circulation. Each effector mechanism is modeled as a low-pass filter in series with a delay. The vagal effector mechanism slows the HR after a 100-ms delay and reaches maximal HR at that time. The beta-adrenergic effector mechanism speeds HR after a 2.5-s delay and then increases to maximal HR 7.5 s later. The alpha-adrenergic effector mechanism begins vasoconstriction after a 5-s delay and then reaches maximal contraction 15 s later. Computer simulations of inhibition of the vagal effector mechanism and activation of the adrenergic effector mechanisms elicit low-frequency oscillations in ABP and HR. These oscillations are similar to those observed experimentally in the dog during hemorrhage. We conclude that the slow temporal response of the alpha-adrenergic effector mechanism controlling TPR is the critical element in predicting the observed low-frequency oscillations in ABP and HR.

Animals↗
PubMed1988

Serologic response to oral polio vaccine and enhanced-potency inactivated polio vaccines.

In a randomized, controlled trial carried out from November 1980 to July 1983 involving 1,114 infants in Baltimore City and in Baltimore and Prince George's counties, Maryland, the serologic response to three doses of two enhanced-potency inactivated polio vaccines was compared with the response to three doses of oral polio vaccine. The mean ages at vaccination were 2.2, 4.7, and 19.9 months, respectively, for the three doses. Seroconversion after the first dose varied from 35% to 84%, and it was higher after oral polio vaccine than after either of the enhanced-potency inactivated polio vaccines for polioviruses types 2 and 3. Approximately two and one-half and 16 months after the second dose, almost all inactivated polio vaccine recipients had antibodies against all three virus types (98-100%). Fewer oral polio vaccine recipients had detectable antibodies to type 1 (89-92%) and to type 3 (96%). After three doses of vaccine, all children had antibodies against types 2 and 3. Approximately 1% of the inactivated polio vaccine recipients and 3% of the oral polio vaccine recipients lacked antibody to type 1. One or two doses of oral polio vaccine stimulated higher reciprocal geometric mean antibody titers against type 2 poliovirus than did the inactivated polio vaccine. For the other two types, the results were mixed. The third dose of inactivated polio vaccine produced significant increases in the reciprocal geometric mean titers against each of the three poliovirus types and resulted in significantly higher reciprocal geometric mean titers after three doses of vaccine for recipients of inactivated polio vaccine than for recipients of oral polio vaccine.

Antibodies, Viral↗
PubMed1988

Analysis of long term heart rate variability: methods, 1/f scaling and implications.

The use of spectral techniques to quantify short term heart rate fluctuations on the order of seconds to minutes has helped define the autonomic contributions to beat-to-beat control of heart rate. We used similar techniques to quantify the entire spectrum (0.00003-1.0 Hz) of heart rate variability during 24 hour ambulatory ECG monitoring. The ECG from standard Holter monitor recordings from normal subjects was sampled with the use of a phase locked loop, and a heart rate time series was constructed at 3 Hz. Frequency analysis of the heart rate signal was performed after a nonlinear filtering algorithm was used to eliminate artifacts. A power spectrum of the entire 24 hour record revealed power that was inversely proportional to frequency, 1/f, over 4 decades from 0.00003 to 0.1 Hz (period approximately 10 hours to 10 seconds). Displaying consecutive spectra calculated at 5 minute intervals revealed marked variability in the peaks at all frequencies throughout the 24 hours, probably accounting for the lack of distinct peaks in the spectra of the entire records.

Adult↗
PubMed1987

Isotopic compositions and probable origins of organic molecules in the Eocene Messel shale.

The sediments that now comprise the Messel shale accumulated 47 +/- 2 million years ago in anaerobic waters at the bottom of a lake. Subsequent depths of burial have not exceeded 300 m, nor has the temperature of the shale exceeded 40 degrees C. Contents of organic carbon reach 25%, and preservation of molecular structures has been excellent. Sixteen different geoporphyrins, including three derived from bacteriochlorophylls of the d series and thus indicative of the existence in the lake of an anaerobic photic zone, have been isolated and identified. Here, we show that the carbon isotopic compositions of these and other biomarkers allow identification of specific sources for some materials and reconstruction of carbon flows within the lake and its sediments. The 13C content of organic matter synthesized by lacustrine primary producers can be estimated from the observed 13C content of the geoporphyrins derived from their chlorophylls. Total organic material in the shale is depleted in 13C by six parts per thousand relative to that input. This difference cannot be explained by selective loss of components enriched in 13C, nor, as shown by isotopic compositions of other biomarkers, by inputs from land plants surrounding the lake or from methanogenic bacteria.

Bacteriochlorophylls↗
PubMed1986

A long-term follow-up study of patients with post-poliomyelitis neuromuscular symptoms.

A "post-polio" syndrome characterized by new neuromuscular symptoms, including muscle weakness, may develop years after recovery from acute paralytic poliomyelitis. We studied 27 patients (mean age, 50.6 years) in whom new muscle weakness developed a mean of 28.8 years after recovery from acute polio. We reevaluated these patients during a mean follow-up period of 8.2 years (range, 4.5 to 20) after they were originally studied at the National Institutes of Health. The total mean follow-up period after the onset of new weakness was 12.2 years (range, 6 to 29). The patients were assessed with quantitative muscle testing, muscle biopsy, electromyography, and virologic and immunologic examination of the cerebrospinal fluid. Muscle strength had declined in all patients. The rate of decline averaged 1 percent per year. The decrease was irregular, with subjective plateau periods that ranged from 1 to 10 years. None of the patients had amyotrophic lateral sclerosis. Oligoclonal bands (IgG) were found in the cerebrospinal fluid of 7 of 13 patients studied, but no specific elevation of antibodies to poliovirus was observed in the cerebrospinal fluid. The newly affected muscles that were evaluated longitudinally with follow-up muscle biopsies and electromyography showed signs of chronic and new denervation. Groups of atrophic muscle fibers (group atrophy) and "neurogenic jitter" were not present. New post-polio muscle weakness is not a life-threatening form of motor-neuron deterioration. It appears that this weakness is not due to a loss of whole motor neurons, as in amyotrophic lateral sclerosis, but that it is due to a dysfunction of the surviving motor neurons that causes a slow disintegration of the terminals of individual nerve axons.

Adult↗
PubMed1986

Immunity against measles and rubella in Massachusetts schoolchildren.

A statewide serosurvey was conducted among 6th, 10th and 12th grade Massachusetts schoolchildren in 1982. Sera were screened using a standard measles hemagglutination inhibition (HI) assay, a sensitive measles plaque neutralization assay, and four rubella assays with corresponding sensitivity limits of approximately 15, 10, 7.5, and 5 international units (IU) of rubella antibody/ml respectively. Using the most sensitive assays, seroprevalence was 98.6% for measles antibodies and 93.1% for any rubella antibodies. For persons who received single doses of either combined measles and rubella vaccines or separate single vaccinations at different times, there were no significant differences in seroprevalence using sensitive assays. Of persons who received combined vaccines, 99.3% had antibody against measles compared to 98.4% of single antigen recipients. For rubella, 98.6% of combined vaccine recipients had antibody compared to 95.7% of single antigen recipients. These seroprevalence data indicate the effectiveness of a combined vaccination program and support epidemiologic data indicating virtual elimination of these diseases in Massachusetts schoolchildren.

Adolescent↗
PubMed1986

Impact of revaccinating children who initially received measles vaccine before 10 months of age.

Two hundred fifty-four infants who had received measles vaccine at less than 10 months of age were revaccinated at greater than or equal to 15 months of age, and their immune responses were compared with 129 control infants who received their first doses of measles vaccine at greater than or equal to 15 months of age. Sera were collected at the time of revaccination (study infants) or primary vaccination (control infants), 3 weeks, and 8 months later and tested for antibody by hemagglutination inhibition (HI), enzyme-linked immunosorbent assay (ELISA), and cytopathic effect neutralization (CPEN). Of the 121 study infants who were initially HI negative, 116 (95.9%) made HI antibody 3 weeks postrevaccination compared with 126 (99.2%) of 127 control infants (P = 0.19). Of the 63 study infants with no initial detectable antibody by any of the three tests, 14 (22.2%) had a measles-specific IgM response 3 weeks postrevaccination compared with 37 of 50 (74.0%) randomly chosen control infants. By 8 months after revaccination, the 121 initially HI-negative study infants were significantly less likely to have detectable HI antibodies than control infants (52.1% v 97.6%) (P less than .001). However, 96.7% of these 121 study infants had detectable neutralizing antibody 8 months postrevaccination, an antibody thought to correlate best with protection. This study confirms the altered immune response to revaccination in infants first vaccinated prior to 10 months of age; however, the data suggest that most of these infants were successfully primed and are probably protected after revaccination.

Age Factors↗
PubMed1985

High effectiveness of aerosolized chick embryo fibroblast measles vaccine in seven-month-old and older infants.

Neither the presence of hypertonic sugar nor the absence of 1% human albumin in the aerosolized chick embryo fibroblast (CEF) measles vaccine was previously found to be responsible for its inadequacy in infants with titers of maternal plaque-neutralizing (PN) antibody at which human diploid cell measles vaccine was immunogenic. Eight weeks after administration of CEF measles vaccine containing 1% human albumin, antibody had developed in all 10 infants 7-10 months old and all 11 children 12-35 months old but in only 26% of 23 infants 3-5 months old and 67% of 9 infants 6 months of age. Failure of antibody development was associated with prevaccination PN antibody titers of greater than or equal to 1:50 (with one exception at a titer of 1:25). The PN antibody response to CEF vaccine (diluted 1:10, approximately 10(5) pfu/ml) in infants under seven months of age (geometric mean titer [GMT], 1:421) was significantly lower (P less than .005) than in older infants (GMT, 1:1,564). At a 1:1,000 dilution of vaccine, only 50% of 10 infants 13-25 months old, 20% of 15 infants 7-10 months old, and none of 8 infants 6 months old developed antibody.

Administration, Intranasal↗
PubMed1984

Successful immunization of infants with and without maternal antibody by aerosolized measles vaccine. II. Vaccine comparisons and evidence for multiple antibody response.

In 4- and 5-month-old infants in whom the undiluted chick embryo fibroblast (CEF) Schwarz strain measles vaccine had a poor immunogenic effect, there was an increase in immunogenicity when the high sugar concentration was diminished without reference to added albumin. The human diploid cell (HDC) measles vaccine was still superior in this age group even in a lower concentration of the Ikić, Edmonston-Zagreb strain of virus. More aerosolized, HDC Ikić strain virus was required for high seroconversion rates in 4- and 5-month-old infants who had higher titers of prevaccination plaque-neutralizing (PN) antibodies. Some of these infants had a delayed immune response that was absent at six weeks but present at three months after vaccination. The data provided evidence that the PN and enzyme-linked immunosorbent assay techniques measured different antibodies that develop and persist in different ways in 4- to 5-month-old infants. The HDC lyophilized measles vaccine yielded unexpectedly high seroconversion rates after subcutaneous injection of 5,000 plaque-forming units (PFUs) in 4-, 5-, and 6-month-old infants: 69%, 89%, and 100% respectively, at 14 weeks. In 12- to 23-month-old infants there was seroconversion of 92% and 100% at six weeks after inhalation of an estimated 175 PFUs of the CEF vaccine and 375 PFUs of the HDC vaccine, respectively. Within six weeks after vaccination, the PN antibody titers were significantly higher with the CEF vaccine (geometric mean titer of 2,275) than with the HDC vaccine (geometric mean titer of 343).

Aerosols↗
PubMed1984

A search for cytomegalovirus and herpes viral antigen in brains of schizophrenic patients.

The peroxidase-antiperoxidase method was employed to search for evidence of cytomegalovirus (CMV) or herpes simplex virus (HSV) antigen in the brains of 25 patients with a diagnosis of schizophrenia, 25 nonschizophrenic neuropsychiatric patients, and 16 nonpsychiatric control subjects. Brain specimens from patients with acute CMV and herpes encephalitis served as positive controls. Although early results with low-titer CMV antisera suggested immunoreactivity in specific brain regions of a small number of schizophrenic and control cases, the present studies with high-titer anti-CMV IgG did not give a positive immunoperoxidase reaction in sections from the basal forebrain, hypothalamus, or midbrain. Scattered neurons in the lateral vestibular nucleus and hippocampus showed questionable staining with CMV IgG in one schizophrenic patient and none in control subjects. No schizophrenic or control cases demonstrated an immune reaction to HSV antisera.

Adult↗
PubMed1984

Immunogenicity of wild and attenuated varicella-zoster virus strains in rhesus monkeys.

Thirty susceptible rhesus monkeys were inoculated with cell-free varicella-zoster virus strain OKA or strain KMcC. Both wild and attenuated strains were used. No clinical signs characteristic of human varicella were seen in any of the animals. Virus was not isolated from throat swabs, blood, or cerebrospinal fluid. Antibodies were measured by an enhanced plaque neutralization test. The wild and attenuated OKA strains produced comparable levels of antibodies for 3 months after inoculation. Attenuated KMcC strains produced lower titers than the wild strain. On rechallenge 3 months after primary inoculation animals boostered with the attenuated OKA strain developed significantly higher antibody titers than animals receiving the wild strain. Animals primed and challenged with the attenuated KMcC strains showed significantly lower antibody titers than animals which received the wild strain. The results indicate that the immunogenicity of attenuated OKA and KMcC strains in rhesus monkeys parallels the experience obtained with these strains in humans.

Animals↗